#ifndef __EXTENTMAP__
  #define __EXTENTMAP__
  
  #include <linux/rbtree.h>

  #define EXTENT_MAP_LAST_BYTE (u64)-4

  #define EXTENT_MAP_HOLE (u64)-3

  #define EXTENT_MAP_INLINE (u64)-2
  #define EXTENT_MAP_DELALLOC (u64)-1

  /* bits for the flags field */
  #define EXTENT_FLAG_PINNED 0 /* this entry not yet on disk, don't free it */

  #define EXTENT_FLAG_COMPRESSED 1

  #define EXTENT_FLAG_VACANCY 2 /* no file extent item found */

  #define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */

  struct extent_map {

  	struct rb_node rb_node;

  
  	/* all of these are in bytes */
  	u64 start;
  	u64 len;

  	u64 orig_start;

  	u64 block_start;

  	u64 block_len;

  	unsigned long flags;

  	struct block_device *bdev;
  	atomic_t refs;

  	unsigned int in_tree:1;
  	unsigned int compress_type:4;

  };

  struct extent_map_tree {
  	struct rb_root map;

  	rwlock_t lock;

  };

  static inline u64 extent_map_end(struct extent_map *em)
  {
  	if (em->start + em->len < em->start)
  		return (u64)-1;
  	return em->start + em->len;
  }
  
  static inline u64 extent_map_block_end(struct extent_map *em)
  {

  	if (em->block_start + em->block_len < em->block_start)

  		return (u64)-1;

  	return em->block_start + em->block_len;

  }

  void extent_map_tree_init(struct extent_map_tree *tree);

  struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,

  					 u64 start, u64 len);

  int add_extent_mapping(struct extent_map_tree *tree,
  		       struct extent_map *em);
  int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em);

  struct extent_map *alloc_extent_map(void);

  void free_extent_map(struct extent_map *em);

  int __init extent_map_init(void);

  void extent_map_exit(void);

  int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len);

  struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
  					 u64 start, u64 len);

  #endif